An Improvement in Tarnish and Corrosion Resistance of 94Ag-4Zn-Cu Alloys with Sn Addition

Abstract:

The tarnish and corrosion resistance of 94Ag-4Zn-Cu-Sn alloys and Ag-5.89Sn alloy compared with Ag-5.95Cu alloy were investigated. The tarnish results show that the DE* value of Ag-5.95Cu alloy is higher than those of 94Ag-4Zn-Cu-Sn alloys and Ag-5.89Sn alloy due to the sulfide formations such as Ag₂S, Cu₂S and CuS. The DE* value significantly decreases with increasing tin content. This is attributed to the matrix enrichment of tin which protects the sulfur reaction on surface. From corrosion test results, 94Ag-4Zn-Cu-Sn alloys and Ag-5.89Sn alloy provide the noble shift in the corrosion potentials and pitting potentials but the negative shift in the corrosion current density compared with Ag-5.95Cu alloy_. Corrosion rate of 94Ag-4Zn-Cu-Sn alloys and Ag-5.89Sn alloy decrease markedly compared with Ag-5.95Cu alloy because it depends on the alloying elements and the microstructural changes. Due to high solubility of zinc and tin, the microstructures of tin-rich alloys consist of the higher portion of single phase and less eutectic structure than that of Ag-5.95Cu alloy.

• Periodical: Advanced Materials Research (Volume 894)
• Pages: 138-142
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.894.138
• Online since: February 2014
• Authors: Jirutthitikalpongsri Hirunyagird, Gobboon Lothongkum, Ekasit Nisaratanaporn
• Keywords: Corrosion, Microstructure, Silver Alloys, Tarnish

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